This distinction is frequently emphasized in online discourse, but I've never found it to be super useful. Pretty much everyone can agree that Ruby on Rails is a framework, while underscore.js is a library, but things get really fuzzy in the middle.

The usual explanation is inversion of control—you call into a library, but a framework calls you. But now that pretty much every language has closures, it's a lot harder to use that as a distinction: is React a library since it all starts with createRoot/render (you called it), or is it a framework because from that point on it's calling you? There are tons of people who are highly opinionated in both directions, which suggests that this dichotomy is artificial and doesn't reflect a deeper reality.